Celebrate Brooklyn has it down--Their free music program is usually what is at Summerstage's not-free fundraising benefits a couple of years later. I can't count the number of mostly unknown bands (mostly local heroes where they came from) the programmers gave a chance to that went on to glory later (like Brazilian Girls). They balance it with big national and international acts too. The staff are all volunteers and have always been nice. The security here is NYPD. They are cool about anything that doesn't break the law and usually seem to enjoy the events as much as the rest of the people. No bouncer attitude. The stage is at the bottom of a small hill. Food and beverage are not cheap, but ok priced (2 Boots), but they are fine if you bring a picnic with no glass bottles or metal cans (they want you to buy wine & beer there) and sit on the grassy hill. Starbucks is a new sponsor and they hand out FREE coffee. The inside viewing area is and is about twice the size of Summerstage. They got rid of the bleachers a few years ago because they were more of an obstruction than a help. But there are still plenty of folding chairs down front. So you can hear and see, even if it gets too crowded for your liking, from either side outside the fence or up on the road. You can dance if you want to. It's 2 blocks from the F train. JUST GO THERE!
Cons: wish they could go through all of August